Compensator for electric circuit breakers



March 1, 1955 F- L. HULBERT 2,703,351-

COMPENSATOR FOR ELECTRIC CIRCUIT BREAKERS Filed June 22, 1955 2shetssheet 1 II. IN V EN TOR.

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COMPENSATOR FOR ELECTRIC CIRCUIT BREAKERS Filed June 22, 1953 2Sheets-Sheet 2 if g2 14 Z] 1; J?

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5 (f LU) ('50 United States atent O COMPENSATOR FOR ELECTRIC CIRCUITBREAKERS Francis L. Hulbert, Dearborn, Mich., assignor to Square DCompany, Detroit, Mich., a corporation of Michigan Application June 22,1953, Serial No. 363,318

7 Claims. (Cl. 200-116) This invention relates to an automatically andmanually operable electric circuit breaker employing a currentresponsivebimetallic member for etiecting automatic operation of thebreaker, and has for its object the provision of a simple, economicaland efiective means for compensating for the movement of the bimetallicmembers of a multipole breaker under the influence of ambienttemperature changes.

Another object of the invention is to provide a single bimetallic memberexposed to the same ambient as a multiplicity of current responsivebimetals in a multipole automatic circuit breaker and compensating forambient temperature changes for all of the current responsive bimetals.

Another object of the invention is the provision of a multipoleautomatic electric circuit breaker having a common crossbar for thepoles of the breaker and a single, releasable member latched by saidcrossbar together with bimetallic members individual to the poles foreffecting movement of said crossbar upon current overload through one ormore bimetals to unlatch said releasable means, with a single bimetallicmember determining the latching engagement between said releasable meansand crossbar and flexing to increase the latching overlap upon a rise inambient in. response to which the current responsive bimetals movetoward unlatching position.

Other objects and features of the invention will be readily apparent tothose skilled in the art from the specification and app-ended drawingillustrating certain preferred embodiments in which:

Figure 1 is a front elevational view of the circuit breaker according:to the present invention, with a portion of the front cover broken awayto show a single outside pole of the breaker.

Figure 2 is a vertical sectional view on the lines 11-41 of Figure 1.

Figure 3 is a perspective view ofthe crossbar of this invention.

It will be understood that the invention herein may be applied to anyautomatic electric circuit breaker usingv a bimetallic member as acurrent responsive element for etieoting automatic tripping and forpurposes of illustration only it is in the drawing shown as. applied toa circuit breaker of the. type described. and claimed in Jackson et a1.Patent No. 2,426,880 granted September 2, 1947, for Circuit Breaker.

The device is shown. as a 3-pole breaker including, as in the patent, acentral pole carrying the operating mechanism and a pair of outsidepoles mounted thereon. The circuit breaker includes a base 1 and a frontcover 2 sealably attached thereto and enclosing stationary contacts 3mounted on terminals 4. extending to the exterior of the breakerenclosure. Cooperating with stationary contacts 3 are movable contactsS'mounted upon the ends of pivotally mounted contact arms 6.

The central contact arm 6 is provided with a slot 7 through whichextends a pin 8 connected to a pair of links 9 and 1-1,.links 11v beingprovidedwith a notch 12 in which is disposed a pin 13 mounted upon anoperating handle 14. Rigidly connected to the central contact arm 6 isan insulating bottom cross plate 15 to which the outer contact arms 6are connected by means of slots in the plate 15 and springs 16 disposedin said slots. A spring 17 has one end connected to pin 8 and itsopposite end connected to a projecting arm 18 rigid with a release lever19 pivoted at 21.

At the top of the breaker is pivotally mounted an in- "ice.

sulating' crossbar 22. Mounted on the crossbar 22 are insulatingabutments 23, one for each pole, here specifically three, and mountedfor engagement with the abutments 23 are a plurality of bimetals 24individualto the poles ofthe. breaker and havinga pair of flexible leads25 connectedbetween thebimetals 24 and the corresponding contact arms 6.A conducting terminal 26 for each. pole extends from the exterior of thebreaker enclosure to the interior thereof and there supportsan end ofeach bimetal 24, the free end of theterminal 26 being indicated at- 27for engagement with the calibrating screw 28,.the end 27 engaging aninsulating pin. 29 at thev extreme free endofthe bimetal 24 as anabutment .to adjust the current-time calibration of the breaker pole.

A U-shaped magnetic yoke 31 embraces eachbimeltal 24 so as to beenergized in response to current flow through the bimetal andcooperatingtherewith for each pole is an individual pivoted armature 32biased to inoperative position by a spring 33 and attractable to theyoke upon the occurrence of a short circuit or heavy overload currentthrough its associated pole to move the crossbar 22 without delayintounlatching position.

The compensator according to the present invention is embodied in abimetallic strip 34 supported upon the crossbar 2-2 by a rivet.3'5.Outside of the bimetal strip 34 is a spring strip 36 parallel therewithand wrapped around its free end, the spring strip. 36 performing onlythe functionof providingv a smooth latching surface for engagement bythe releasable member 19. The bimetal strip 34 is mounted so that itflexes in the same direction as the bimetals 24, but, being located onthe opposite side of the pivot 37 of the crossbar 22, its motion effec:tively. subtracts from the. ambient temperature movement of thecurrentresponsive bimetals; thus, as viewed in Fig.- ure 2, bimetals24tend to move downwardly as they are heated due-to ambient and, hence,rotate crossbar 22in clockwise direction toward unlatching position.However, this increased ambient temperature also moves the free end ofthe bimetal 2.4 downwardly and this is effected in. acounterclockwisedirectionrelative to the pivot 37 so that the movement of the bimetalstrip 34 tends to incrigse' the latching. overlap with the releasablemember As shown in FigureZ,v the bimetalstrip 34 and the cur.- rentresponsive bimetals24-have been heated by the ambient so that if thestrip 34 were not thermally responsive and were tight against thecrossbar 22, it would be sub.- stantially in tripping position. However,due to the flexure of the bimetal strip 34, it has moved downwardly toprovide a substantial overlap. The pin 38.is provided on the releasablemember 19 to. determine the maximum overlap between the bimetal stripand the releasing member 19 and is effective primarily inthecalibrationof the breaker.

The operation of the breaker is more fully described in the Jackson etal. patent cited above, the parts being shown in Figure 2 in the Onposition and movable to Ofi. position by a counterclockwise rotation ofthe handle 14 which collapses the links 9 and 11, the contact arms 6thereafter moving counterclockwise to open position under. the bias ofspring 17.

Upon the occurrence of a current overload or short circuit currentthrough any one or more poles of the breaker, the crossbar 22 will berotated in a clockwise direction under the action of the associatedbimetal and/or armature for the pole or poles carrying the overload orshort circuit, and will release the member 19 which then carries thespring 17 overcenter and also positively engages the central con-tactarm 6 to collapse the toggle and move all of the arms6 into Offposition. Releasable member 19 is movedv to relatched position by movingthe handle in a counterclockwise direction to Oii position and then theparts may be returned to the On position of Figure 2 by a clockwiserotation of the handle.

With the present invention, it is seen that there is provided a simpleand effective ambient temperature compensation in a multipole automaticelectric breaker in which there is employed a single bimetal strip whichcompensates for ambient temperature changes on a multiplicity of currentresponsive bimetals therewith individual to the poles of the breaker,the single compensating bimetal strip functioning regardless of thenumber of breaker poles provided.

While certain preferred embodiments of the invention have beenspecifically disclosed, it is understood that the invention is notlimited thereto, as many variations will be readily apparent to thoseskilled in the art and the invention is to be given its broadestpossible interpretation within the terms of the following claims.

What is claimed is:

1. In a multipole manual and automatic electric circuit breaker, aplurality of pairs of stationary and movable contacts for the breakerpoles, manual means for effecting engagement and disengagement of saidcontacts at will, means for effecting automatic separation of saidcontacts upon the occurrence of a current overload through any one ormore of the breaker poles including a current responsive bimetal foreach of the breaker poles and means rendering said bimetals responsiveto the passage of current through their associated breaker poles, meansreleasable to effect automatic separation of said contacts, saidbimetals controlling the release of said means, a single bimetal stripdisposed in the same ambient temperature as the current responsivebimetals, and means whereby the flexing of said single bimetal stripcompensates for the flexing of all said current responsive bimetals uponchange in ambient temperature so that their control of the release ofsaid releasable means is substantially independent of said ambient.

2. In a multipole manual and automatic electric circuit breaker, aplurality of pairs of stationary and movable contacts for the breakerpoles, means for effecting automatic separation of said contacts uponthe occurrence of a current overload through any one or more of thebreaker poles including a current responsive bimetal for each of thebreaker poles, a crossbar common to all the breaker poles and adapted tobe moved by the flexing of one or more of the bimetals, means renderingsaid bimetals responsive to the passage of current through theirassociated breaker poles, means operable by said crossbar to effectautomatic opening of said movable contacts, a single bimetal stripcontrolling the operation of said last mentioned means by said crossbar,and means whereby flexing of said single bimetal strip compensates forthe movement of all said current responsive bimetals in response tochanges in ambient temperature within the breaker.

3. In a multipole manual and automatic electric circuit breaker, aplurality of pairs of stationary and movable contacts for the breakerpoles, means for effecting automatic separation of said contacts uponthe occurrence of a current overload through any one or more of thebreaker .poles including a current responsive bimetal for each of thebreaker poles, a crossbar common to all the breaker poles and adapted tobe moved by the flexing of one or more of the bimetallic members, meansrendering said bimetal members responsive to the passage of currentthrough their associated breaker poles, means releasable to eifectautomatic opening of said movable contacts, a single bimetal stripcontrolling the operation of said releasable member by said crossbar andflexing to compensate for the movement of all said bimetallic members inresponse to changes in ambient temperature within the breaker, saidcompensating bimetal strip being mounted upon the common crossbar andlatching said releasable means.

4. In a manual and automatic electric circuit breaker, a plurality ofpairs of stationary and movable contacts for the breaker poles, meansfor effecting automatic separation of said contacts upon the occurrenceof a current overload through any one or more of the breaker polesincluding a current responsive bimetal for each of the breaker poles, acrossbar common to all of the breaker poles, a latching surface on saidcross bar, means normally engaging said latching surface and releasablethereby to effect automatic separation of said contacts, and a singlebimetal strip carried by the crossbar and controlling the overlapbetween said latching surface and said releasable means, said stripbeing faced so as to increase the overlap upon increase in ambienttemperature.

5. In a multipole manual and automatic electric circuit breaker, aplurality of pairs of stationary and movable contacts for the breakerpoles, means for effecting automatic separation of said contacts uponthe occurrence of a current overload through any one or more of thebreaker poles including a current responsive bimetal for each of thebreaker poles, a crossbar common to all the breaker poles and adapted tobe moved by the flexing of one or more of the bimetallic members, meansrendering said bimetal members responsive to the passage of currentthrough their associated breaker poles, means releasable to effectautomatic opening of said movable contacts, a single bimetal stripcontrolling the operation of said releasable member by said crossbar andflexing to compensate for the movement of all said bimetallic members inresponse to changes in ambient temperature within the breaker, saidcompensating bimetal strip being mounted upon the common crossbar andlatching said releasable means, means pivotally mounting said crossbarfor rotation about a point intermediate the front and back edgesthereof, abutment surfaces at one side of said pivotal mountingengageable by said current responsive bimetals and said compensatorstrip being mounted so that its free end operates at the opposite sideof said pivotal mounting and is movable away from said crossbar upon anincrease in ambient temperature.

6. In a multipole automatic electric circuit breaker, a plurality ofpairs of stationary and movable contacts for the breaker poles, meansfor effecting automatic separation of said contacts upon the occurrenceof a current overload through any one or more of the breaker polesincluding a current responsive bimetal for each of the breaker poles, acrossbar common to all the breaker poles and adapted to be moved by theflexing of one or more of the bimetals, means rendering said bimetalmembers responsive to the passage of current through their associatedbreaker poles, means releasable to effect automatic opening of saidmovable contacts, a single bimetal strip mounted on said crossbar andlatching said releasable means and flexing to compensate for themovement of all said current responsive bimetal members in response tochanges in ambient temperature within the breaker, and a spring stripmounted generally parallel to said compensator strip and enclosing thelatching end thereof to provide a smooth latching surface engageable bysaid releasable means.

7. In a multipole automatic electric circuit breaker, a plurality ofpairs of stationary and movable contacts for the breaker poles, meansfor effecting automatic separation of said contacts upon the occurrenceof a current overload through any one or more of the breaker polesincluding a current responsive bimetal for each of the breaker poles, acrossbar common to all the breaker poles and adapted to be moved by theflexing of one or more of the bimetals, means rendering said bimetalmember responsive to the passage of current through their associatedbreaker poles, means releasable to eifect automatic opening of saidmovable contacts, a single bimetal strip mounted on said crossbar andlatching said releasable means and flexing to compensate for themovement of all said bimetallic members in response to changes inambient temperature Within the breaker, means pivotally mounting saidcrossbar for rotation about a point intermediate the front and backedges thereof, abutment surfaces at one side of said pivotal mountingengageable by said current responsive bimetals, said compensator stripbeing mounted so that its free end operates at the opposite side of saidpivotal mounting and is movable away from said crossbar upon an increasein ambient temperature.

References Cited in the file of this patent UNITED STATES PATENTSKrieger Feb. 29, 1944

